This invention relates to an apparatus for delivering work pieces to successive work stations and more particularly to a positioning apparatus provided with means for positively and precisely locating work pieces throughout successive manufacturing steps.
Automated manufacturing systems having successive synchronized work operations are well known in the art. Typically, a transfer apparatus is provided wherein a plurality of pallets or platens are secured to a common conveyor such as a chain so that they are precisely located on the conveyor relative to each other. With such an apparatus, the platens are driven by the conveyor, generally in an indexing mode, to a plurality of successive work stations wherein work pieces on the platens are manually or automatically processed at the work station. When the work pieces are processed automatically, it is essential that the platen supporting the work piece be precisely located relative to the work station so that the desired processing of the work piece can be completed. A common means for attaining the desired precision is to accurately assemble the platens on a chain by rigidly fixing the platens to the chain at precise locations so that when the chain is indexed during use, the platen and the work piece thereon will be precisely located at the work station. This solution has proven to be less than satisfactory since the accuracy demanded during manufacture renders manufacture of such a construction time consuming and expensive. In addition, during use of such a construction, the chain gradually becomes worn and/or stretched over a relatively short period of time thereby causing the platens to become misaligned relative to the work stations. This requires that the chain-platen portion of such an apparatus be replaced within a relatively short time. Alternatively, it has been proposed to attain precise positioning of the platens by an arrangement which includes contact bushings in the platen and stop-pins which are arranged to mate with the bushing. The stop-pins are adapted to move in a vertical path to enter and exit the bushings thereby effecting desired positioning of the platens. This arrangement requires individual actuating means for each set of stop-pins associated with individual platens, since the stop-pins require an essentially vertical path. Thus, this arrangement is undesirably expensive due to the required individual controls and individual means for moving the stop-pins into registry.
Thus, it would be desirable to provide a means for accurately positioning platens adapted to support a work piece which does not require accurate positioning of the platen on a conveyor or chain during manufacture. Furthermore, it would be desirable to provide a positioning means having common controls and actuating means for all such positioning means associated with the individual platens.